Re: [PATCH] USB: power-management.txt - disconnect clarification

[Alan Stern <stern@rowland.harvard.edu>]

On Mon, 12 Nov 2007, Tilman Schmidt wrote:

> From: Tilman Schmidt <tilman@imap.cc>
> 
> Add a paragraph to Documentation/usb/power-management.txt about the
> interaction between suspend and disconnect.
> 
> Signed-off-by: Tilman Schmidt <tilman@imap.cc>
> ---
> 
> --- linux-2.6/Documentation/usb/power-management.txt	2007-10-14 00:41:08.000000000 +0200
> +++ linux-2.6.24-rc2-work/Documentation/usb/power-management.txt	2007-11-12 10:27:30.000000000 +0100
> @@ -278,6 +278,12 @@
>  	(although the interfaces will be in the same altsettings as
>  	before the suspend).
>  
> +If the device is disconnected or powered down while it is suspended,
> +the disconnect method will be called instead of the resume or
> +reset_resume method.  This will also happen if the system is resumed
> +from hibernation, as the device could have been disconnected without
> +the system being able to detect it.
> +

I don't like the second sentence very much.  How about something like 
this instead:

+If the device is disconnected or powered down while it is suspended,
+the disconnect method will be called instead of the resume or
+reset_resume method.  This is also quite likely to happen when
+waking up from hibernation, as many systems do not maintain suspend
+current to the USB host controllers during hibernation.  (It's
+possible to work around the hibernation-forces-disconnect problem by
+using the USB-Persist facility, described in
+Documentation/usb/persist.txt.)

Alan Stern

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